Guard timer to optimize e911 call handling

ABSTRACT

Systems and methods for optimized call handling during e911 calls. Normally, when a user equipment (UE) is connected to a public safety answering point (PSAP)—e.g., is on a 911 call—all incoming calls are automatically routed to voicemail. In contrast, the systems and methods disclosed herein enable calls that were dialed within a predetermined time window of the 911 call to be sent through to call-waiting to enable the user to accept or reject the call. The system can use a “guard timer” to determine whether a call is within the predetermined time window. The system can include a single guard timer for all incoming calls—e.g., “any call made from the UE within the previous X minutes prior to the 911 call.” The system can also include individual guard timers for each call that expire separately relative to the call&#39;s proximity to the 911 call.

CROSS REFERENCE TO RELATED APPLICATIONS

The present disclosure is a continuation of, and claims priority under35 U.S.C. § 120 to, U.S. patent application Ser. No. 15/665,272, filedJul. 31, 2017, which is a non-provisional of, and claims priority under35 USC § 119(e) to, U.S. Provisional Patent Application No. 62/476,367,filed Mar. 24, 2017, the entire disclosures of which are herebyincorporated by reference in their entirety.

BACKGROUND

The enhanced 911 (e911) service was developed in response to theincreasingly mobile nature of modern communications. e911 enables a userto dial 911 and be connected to the appropriate emergency servicesregardless of their location. Obviously, there cannot be a singlecallback number because a cellular caller who hails from Atlanta, Ga.,but calls 911 while they are in New York City, N.Y. does not want to beconnected to emergency services in Atlanta. To this end, someenhancements were needed to enable callers to be ready for localemergency callback services based on any location.

Currently, if a user dials 911 from a cellular or internet protocol (IP)based communications device (e.g., a cell phone, smart phone, laptop,tablet, etc.), they are routed to local emergency services using thelocation provided by the cell tower or wireless router to which they areconnected. Due to the somewhat limited range of both of thesecommunications methods, the location provided is generally specificenough for routing purposes. In other words, in most cases, the areacovered by a particular cell tower, for example, is also covered by asingle, or a small number of, emergency service providers. Thus, thenetwork may have primary and secondary PSAP locations for the samelocation and cell tower, for example, with different callback numbersfor each PSAP location.

When a user dials 911, however, the user is generally unable to receivecalls or call-waiting notification—all calls including PSAP callbackfrom previous 911 call attempt are automatically rejected by the userequipment (UE) and/or the network. In addition, no explanation isprovided to incoming callers as to why the call was rejected. Generally,the call simply rings or goes immediately to voicemail.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items or features.

FIG. 1 depicts an example of a system for optimized call handling duringenhanced 911 (e911) calls including a user equipment (UE) connected toan Internet Protocol Multimedia Core Network Subsystem (“IMS”) withmultiple caller categories, in accordance with some examples of thepresent disclosure.

FIG. 2 is a flowchart depicting an example of a first method using aretroactive guard timer to optimize call handling during e911 calls, inaccordance with some examples of the present disclosure.

FIG. 3 is a flowchart depicting an example of a method for usingmultiple proactive guard timers to optimize call handling during e911calls, in accordance with some examples of the present disclosure.

FIG. 4 is a flowchart depicting an example of a method usingcaller-specific guard timers to optimize call handling during e911calls, in accordance with some examples of the present disclosure.

FIG. 5 is an example of a UE for use with the systems and methodsdisclosed herein, in accordance with some examples of the presentdisclosure.

FIG. 6 is an example of a network server for use with the systems andmethods disclosed herein, in accordance with some examples of thepresent disclosure.

FIG. 7 is an example of a cellular and internet protocol network for usewith the systems and methods disclosed herein, in accordance with someexamples of the present disclosure.

FIG. 8 is an example of an Internet Protocol Multimedia Core NetworkSubsystem (“IMS”) for use with the systems and methods disclosed herein,in accordance with some examples of the present disclosure.

DETAILED DESCRIPTION

As mentioned above, currently, when a user dials 911 from a device thatutilizes enhanced 911 (e911) services such as, for example, a cellphone, smart phone, laptop, or tablet computer, that devices cannotsimultaneously receive another call. In other words, in an effort toprotect users from distractions during an emergency, the user equipment(UE) and/or network disables call-waiting and/or other features. If acaller calls the user during an e911 call, therefore, the call simplyrings from the caller's side or is sent straight to voice-mail. The useris unaware that the caller has called.

This feature can prevent users from being distracted during a 911 calland from accidentally hanging up on emergency services during a 911 callas they try to switch between the incoming call and the 911 call, amongother things. There may be times, however, when the user would like toreceive an important call even though they are on a 911 call. Indeed, insome situations, the incoming call may resolve the issue about which theuser is calling 911 in the first place.

One example is when a user calls a public safety answering point(PSAP)—i.e., the service provider that is called when the user dials911—and hangs up, is put on hold, or is disconnected. The user may thenredial the PSAP in an attempt to complete the call. In the meantime,based on the previous call (i.e., caller ID) from the user, the PSAP mayattempt to call the user back. In this case, it would be convenient forthe user to be able to hang up the second 911 call and take the incomingcall from the PSAP. This can avoid both (1) the delay associated withcalling the PSAP back on the second call and any associated hold timeand (2) the redundancy of two emergency operators connected with thesame caller on two different lines.

In a similar scenario, a user may call his doctor in an emergencysituation with which the doctor is already familiar (e.g., a heartcondition). When the call goes unanswered, the user may then dial 911.If, while the user is on the call with 911, the doctor calls back, itwould be useful to notify the user to this fact. The user may be able tohang up with 911 and speak to the doctor, which may enable a moreefficient resolution of the pending emergency. The doctor may be able torecommend a dosage change, or other solution, that at least temporarilyresolves the issue.

As another example, a user may call a child's cell phone, for example,looking for the child. If the user is unsuccessful for some period oftime, the user may call 911 to report the child missing. Obviously, ifthe child calls the user during the 911 call, it would be beneficial forthe user to receive that call. This would obviously be a relief for theparent of a missing child, but can also prevent emergency resources frombeing unnecessarily committed. The user could simply receive the callfrom the child and “cancel” the report to 911.

To this end, it would be useful for call-waiting (and perhaps otherfeatures) to be enabled for recently dialed calls. So, for example, if auser dials a first call and then hangs up and dials a second call to911, then a retroactive “guard timer” can be activated. The retroactiveguard timer basically says, “any call that was made in the previous Xamount of time prior to this 911 call will be put through, all othercalls will be handled in the usual manner (e.g., sent directly tovoicemail).” This may be based purely on the call history log of theuser's UE, for example.

If the first caller calls back within the predetermined time associatedwith the retroactive guard timer, then that caller can be put through tothe user (e.g., to call-waiting), even though the user is currently on a911 call. Calls that were made outside the retroactive guard timer cansimply ring, be sent directly to voicemail, etc.—i.e., however calls arenormally handled when a user places a 911 call (the “usual manner”). So,for example, assume the retroactive guard timer is set to 180 secondsand the user calls Caller 1 at 09:45:30 AM, Caller 2 at 10:27:35 AM, andthen calls 911 at 10:27:55 AM. If Caller 1 calls the user back while theuser is on a 911 call, then Caller 1 is handled in the usual manner.Caller 2, on the other hand, is put through because 25 seconds (the timebetween the call to Caller 1 and the 911 call) is within the 180 secondretroactive guard timer.

It may also be useful, however, to have a proactive guard timer. Inother words, if the user dials 911 and hangs up, a proactive guard timeris triggered. If the user then calls 911 again, any call that comes insubsequent to the second 911 call and within the proactive guard timerlimit (e.g., 180 seconds) is put through to the user. So, as an example,if the user calls 911 at 10:27:30 AM and then hangs up at 10:27:55 AM, aproactive guard timer is started based on the user hanging up the first911 call. If the user then calls 911 again at 10:28:45 AM, all callsthat come in until the guard timer expires at 10:30:55 AM (180 secondsfrom when the user hung up from the first 911 call) will be put through.After 10:30:55 AM, if the user is still on the 911 call, all calls willbe handled in the usual manner. This may be useful as it is likely thatCaller 2 is the PSAP calling back based on the initial 911 call.

Example of the present disclosure, therefore, can comprise a guard timersystem 100 to enable call-waiting to be enabled for (1) recently dialednumbers within a retroactive guard timer when a user is on an e911 callor (2) calls within a proactive guard time when a user is on a seconde911 call—rather than just being sent to voicemail or disconnected. Asshown, the UE 102 can connect to the Internet Protocol Multimedia CoreNetwork Subsystem (“IMS”) 104 via one or more cell towers 106 (for acellular call) or a wireless router 108 (for an internet protocol, orIP, call), among other things. As mentioned above, however, when the UE102 is connected on an e911 call, the UE 102 is generally unable toreceive calls because call-waiting is inactive. This is intended toprevent the user from accidentally hanging up in the emergency call, orotherwise be distracted during an emergency.

For some callers, however, it may be desirable to inform the user (viathe UE 102) that the caller is someone the user recently tried tocontact. This can enable the user to accept the incoming call, ifdesired. In the example above, if the caller is redialing 911 and theincoming call is the PSAP calling back, for example, the user may wishto hang-up on the current call to take the incoming call from the PSAP.Thus, the user is connected directly to the PSAP, saving the time ofwaiting for another operator on the second 911 call, and the PSAP issaved from having two operators connected to the same user at the sametime.

In some cases, the guard timer system 100 can be a function of the UE102. In other words, an application (“app”) or the operating system (OS)of the UE 102 can include a feature that detects when the user dials911, disables call-waiting in general, and enables the guard timer.Thus, when a caller 110 calls during an e911 call, the UE 102 canautomatically either send the caller 110 to voicemail or activatecall-waiting, for example, depending on whether the user previouslytried to contact the caller. Thus, most calls can be handled in theusual manner, while call-waiting can be activated for the user'scardiologist who the user tried to call two minutes ago, for example.

In other examples, guard timer functionality can be controlled by theIMS 104. A number of “back-end” components of the IMS 104 could beresponsible for determining whether the user recently dialed a caller,determining that the guard timer has not expired, and then activatingcall-waiting as appropriate. In other examples, the mobile switchingcenter (MSC), which handles end-to-end connections anyway, could be usedto maintain the guard timer, check the call history, and route the calleither directly to voicemail or to the UE 102 with a code (e.g., asession initiation protocol (SIP) code) to trigger call-waiting on theUE 102. In other words, because the MSC generally handles routing forvoice calls, the MSC may already be aware that the user has dialed 911.Thus, the MSC can detect that the user has dialed 911, check the guardtimer, and check the caller against the call history—e.g., the list ofcalls placed within the predetermined guard timer window and then actaccordingly.

In other examples, the system 100 can be a function of a telephoneapplication server (TAS). In some examples, when a user dials 911, theTAS can receive a message (e.g., a SIP message) indicating that the UE102 is connected to a PSAP. If a user receives a call during this time,the TAS can determine if a guard timer is set and, if so, compare thecaller to the history of recent callers. While the user is connected tothe PSAP, therefore, only calls from a sufficiently recent caller causethe call-waiting on the UE 102 to be activated. Other callers who theuser has not dialed called or dialed recently are handled in the usualmanner.

It should be noted that, at present, there is no SIP message thatenables the UE 102 to inform the network that the UE 102 is on a 911call. The closest facsimile is the generic 486 code that merelyindicates that the UE 102 is “busy.” The call-handling (i.e., sendingcalls to voicemail) while the UE 102 is on a 911 call is, for example,generally handled by the UE 102. The network simply routes the call tothe UE 102 as per normal.

To this end, examples of the present disclosure also include a new,updated SIP response code or SIP header that indicates the UE 102 is ona 911 call. Thus, in some examples, the SIP message can include thestandard 486 “busy” code, but also include a header (e.g., “911”)indicating the UE 102 is busy because the UE 102 is on a 911 call. Inother examples, a separate, new, currently unused, SIP response code(e.g., 475) can be used to indicate that the UE 102 is on a 911 call.

When the UE 102 disconnects from the PSAP, the TAS can receive a secondSIP message reenabling call-waiting to its normal operation (i.e., allcalls can invoke call-waiting) and any other disabled functions. Ofcourse, other components of the IMS 104 such as the Third-GenerationPartnership Project (3GPP) Authentication, Authorization, and Accounting(AAA), home location register (HLR), or home subscriber serve (HSS),among others could also include this feature.

Obviously, the user can call both PSAPs 110 a and “normal” callers 110 bfrom the UE 102. It is only the calls to PSAPs 110 a (e.g., calls to911), however, that trigger the guard timer system 100. The firstcategory 110 a can be used to identify when the user is connected to aPSAP. Thus, the first category 110 a can include, for example, theactual number dialed to reach e911 services (e.g., 911 in the U.S. and999 in the UK) and actual local numbers for PSAPs. Thus, when the userdials any number in the first category 110 a, the guard timer system 100is activated. If a user then receives a call from a normal caller 110 b,the system 100 can determine if the normal caller 110 b was calledwithin the guard timer 112 limit (either retroactively or proactively,as discussed below).

As the name implies, the guard timer 112 is literally a time limit anddictates whether a normal caller 110 b is put through when the user ison a 911 call or handled in the usual manner. So, if the guard timer 112is set to two minutes, for example, then at the moment the user dials911, any call in the call history in the previous two minutes will beput through, other calls will no. Of course, two minutes is only anexample and the guard timer 112 could be any length of time set by, forexample, the user, the service provider or the manufacturer of the UE102.

In some examples, the second category 110 b can include a fixed list ofcallers. In other words, any call that was made in the two minutes priorto placing the 911 call is put through to the UE 102 for the duration ofthe 911 call. Any caller 110 b who was not called in the last twominutes is handled in the usual manner. If the user made three calls inthe two minutes prior to the 911 call, for example, then a call from acaller 110 b associated with any of those three calls will be putthrough.

In other examples, the guard timer 112 can “expire” for each call basedon its actual timestamp. In other words, a call placed immediatelybefore the 911 call will be put through for the first two minutes of the911 call, but a call placed one minute prior to the 911 call will onlybe put through for the first minute of the 911 call—at which point thetwo-minute guard timer 112 expires for that call. In this scenario, oncethe user has been on the 911 call for two minutes, the guard timer 112will have expired for all calls and all calls with be handled in theusual manner.

In some cases, all calls received from callers in the first category 110a (PSAPs) can be put through to call-waiting irrespective of the guardtimer 112. In this configuration, the guard timer 112 only applies tonon-PSAP, or normal callers 110 b. Thus, any caller that is in the firstcategory 110 a (a PSAP) and any caller in the second category 110 b thatis within the guard timer 112 window can be put through to call-waitingon the UE 102, while all other callers 110 b are handled in the usualmanner.

In a scenario where a user calls 911, hangs up, and then calls 911again, for example, an operator may call the UE 102 back based on thefirst call (where the user hung-up). In this scenario, the operator canbe put through to the user because the first call to 911 is within theguard timer 112 window and/or because the call is in the first category110 a. In this manner, the user may be able to hang up on the second 911call—which may be on hold or in queue—and answer the incoming call fromthe PSAP operator. This enables the user to be connected to the PSAP 110a more quickly and clears a call from the queue at the PSAP 110 a at thesame time.

Of course, depending on the situation, the user may choose to (1) acceptthe incoming call and place the current (911) call on hold, (2) acceptthe incoming call and hang up the current (911) call, or (3) reject theincoming call. If a user dials 911 to report a missing child, forexample, the user is not likely to accept a call from their cardiologisteven if the user has called the cardiologist within the guard timer 112window. A user who calls 911 to report a possible heart attack, on theother hand, may accept the call from the cardiologist and either placethe 911 call on hold or disconnect from it. The user's cardiologist mayinsist that the user hang up and dial 911, for example. In this case,the user can simply switch back to the second 911 call already on hold.Regardless, the guard timer system 100 provides the user with thechoice.

Thus, the first category 110 a can include a list of local numbers foremergency providers (e.g., police, fire, emergency medical services(EMS), etc.) that are likely to call back in an emergency. In otherwords, when a caller dials 911, the PSAP 110 a routes the call to theappropriate emergency service. When a PSAP 110 a calls the user back,however, the PSAP 110 a is generally calling from a local number. Thus,the caller ID, for example, for the call from the PSAP 110 a is not“911,” but some local phone number. Thus, the first category 110 a caninclude all local numbers for PSAPs in, for example, the county, city,area, state, or region.

As shown in FIG. 2, therefore, examples of the present disclosure cancomprise a method 200 for providing a retroactive guard timer foroptimized call handling during an e911 call. In its simplest form, themethod 200 simply puts through any calls made in the last “X” minutes orseconds prior to the 911 call and handles all other calls in the usualmanner. In this configuration, an application (“app”), the OS, or othersoftware on the UE 102 can monitor calls and activate or deactivatecall-waiting, as necessary. Thus, rather than simply sending a caller110 to voicemail, for example, some callers 110 can be put through tocall-waiting to enable the user to choose whether to take the call, ornot.

At 202, the UE 102 can place a first call to a PSAP 110 a. In the US,regardless of how the user places the call (e.g., cell phone, landline,tablet, etc.), this is generally achieved by dialing 911. In the UK,this is generally achieved by dialing 999. Other countries may use othercodes or sequences. Regardless, as mentioned above, dialing 911, forexample, currently activates special call handling, where all incomingcalls are sent directly to voicemail. Thus, the UE 102 essentiallyenters “do not disturb” mode automatically.

In contrast, dialing 911 in this case can invoke the method 200 forproviding optimized call handling during an e911 call, described herein.Thus, the user dialing 911 activates the app or script responsible formonitoring incoming calls and taking an appropriate action. The app canuse a listening function, for example to detect when the dialer on theUE 102 dials 911. In other examples, the app can monitor the transceiverto detect when the UE 102 connects to a PSAP. In some examples, the UE102 can also include a list of local numbers associated with PSAPs(e.g., where 911 service is not available).

At 204, the UE 102 can receive a second call at the transceiver.Conventionally, with the UE 102 connected to the PSAP 110 a, the UE 102(or the network) would simply handle the second call in the usualmanner. In this case, however, the method 200 can determine if theincoming call is a caller that was dialed within a predetermined amountof time prior to the 911 call—or within the retroactive guard time. Acaller that the user has not dialed within the predetermined amount oftime can still be handled in the usual manner. Recent calls, on theother hand, can activate call-waiting to give the user the option totake the call. In this manner, the user is not distracted by randomcalls, for example, during an emergency, but may receive calls fromcallers that the user was recently attempting to contact.

To this end, at 206, the method 200 can retrieve the call history forcalls within the retroactive guard timer (e.g., within the last twominutes). In some examples, this can be achieved by consulting thebuilt-in call history log found in most UEs 102. In other examples, arunning call list can be stored in an app for use in this scenario. Instill other examples, the app may simply look at the timestamps of thecalls in the call history log of the UE 102 and select the appropriatecalls.

At 208, the app can determine if the second call is from a caller thatwas called prior to the 911 call and within the retroactive guard timer.Thus, callers that the UE 102 dialed outside the retroactive guard timerand callers that simply have never been dialed from the UE 102 arehandled in the usual manner, while calls from callers within theretroactive guard timer are sent through to the UE 102. If theretroactive guard timer is set to five minutes, for example, a numberdialed on the UE 102 four minutes before the 911 call would be putthrough to call-waiting, while a call made six minutes before the 911call would be sent straight to voicemail.

At 210, if the second call is a caller that was called recentlyenough—i.e., within the retroactive guard timer—the app can activatecall-waiting. As normal, the call-waiting can include the name and/ornumber of the caller to enable the user to decide whether to reject oraccept the call.

In some cases, the call from Caller 1 may be coming from a PSAP 110 acalling from an unknown local number. In other words, if the user dialed911, hung up, and then dialed 911 again, then Caller 1 may be the PSAP110 a calling back due to the first call to 911. Because the PSAP 110 ais likely calling from a local number, however, the call-waiting willnot necessarily say “911,” but rather will display the local number(e.g., 404-555-1212). To this end, in some examples, all incoming PSAPcalls can include a code or message (e.g., a SIP message) that causesthe UE 102 to display “911,” “PSAP,” “Emergency Services,” or some otherindication of who is calling. This gives the user some indication of whois calling, though the user may not recognize the number.

At 212, the method 200 (e.g., an app) can determine if the user acceptedthe call or rejected the call (or simply let it go to voicemail). At214, if the user chose to accept the incoming call, then the normalcall-waiting functions can be available to the user. In other words, theuser can choose to reject the second call, take the second call andplace the first call on hold, or take the second call and hang up thefirst call, among other things. If the user is a family member, the usermay wish to switch over, leaving the 911 call on hold, quickly tell thefamily member what is going on, and the switch immediately back to the911 call—hopefully in an effort not to miss the PSAP operator.

At 216, if the caller 110 b was not called by the UE 102 within theretroactive guard timer or the user rejects the second call or lets itgo to voicemail, the caller 110 b can be sent to voicemail to enable thecaller to leave a message. Thus, ultimately, the caller ends up invoicemail; however, the user has at least been provided with theopportunity to answer calls from those callers who were dialed recentlyfrom the UE 102. In either case, the caller can leave a message asnormal.

As shown in FIG. 3, examples of the present disclosure can comprise amethod 300 for providing multiple caller-specific guard timers foroptimized call handling during an e911 call. As mentioned above, asomewhat more complicated approach is to maintain a separate guard timerfor each call made from the UE 102. In other words, rather than justincluding “all calls made in the last 5 minutes prior to the 911 call,”for example, the system can put through all calls made in the last fiveminutes from the present time based on a specific guard timer for eachseparate call made prior to dialing 911. In this manner, for afive-minute guard timer, for example, the caller-specific guard timerfor a call made one minute prior to the 911 call, for example, willexpire four minutes into the 911 call. The caller-specific guard timerfor a call made three minutes prior to the 911 call, on the other hand,will expire two minutes into the 911 call. Of course, five minutes isused merely as an example, and other predetermined time windows could beused.

To this end, at 302, the user can place a call to Caller 1 at a firsttime (302A) and a call to Caller 2 at a second time (302B). At 304, acaller-specific guard timer for each call can be set. In this case, at304A, caller-specific guard timer 1 can be set for call 1. Similarly, at304B, caller-specific guard timer 2 can be set for call 2. As above,this can be done by checking the call history of the UE 102 in responseto the user calling 911, for example, or can simply be a running list ofrecent calls that are within the predetermined call window. In otherwords, the app can maintain a running list of all calls made in the lastfive minute, which changes over time as calls drop off and new calls aremade. In its simplest form, however, the app can simply refer to the“recent calls” list maintained on most UEs 102.

At 306, the user can place a call to the PSAP 110 a. As mentioned above,this may be achieved by dialing 911, for example, or dialing theappropriate local number or code for PSAPs 110 a in the user's area. At308, the UE 012 can receive an incoming call from Caller 1. Normally,the IMS 104 would simply route the call to the UE 102 and, if the UE 102were on an emergency call, the UE 102 would automatically send the callto voicemail. In this case, however, how the call is handled depends onwhether the caller-specific guard timer for that particular number hasexpired or not.

At 310, the method 300 can determine if the caller-specific guard timerfor that call has expired or not. In this case, because the incomingcall is from Caller 1, this involves determining if caller-specificguard timer 1 has expired. Of course, if the call is from anyone otherthan Caller 1 or Caller 2 (and perhaps a PSAP 110 a, as discussedabove), then the call is automatically handled in the usual mannerbecause the call would not have a guard timer set. In this case, whilecaller-specific guard timer 1 and caller-specific guard timer 2 wereboth set to five minutes, they were started at different times (e.g.,call 1 was placed before call 2) and thus, expire at different times. Ifcall 1 and call 2 were placed one minute apart, for example, thencaller-specific guard timer 1 would expire one minute beforecaller-specific guard timer 2.

At 312, if caller-specific guard timer 1 has not expired, the method 300can send the call through to the UE 102, activating call-waiting. Thus,the user is given the opportunity to accept or reject the call—eventhough they are on an emergency call.

At 314, the method 300 can determine if the user accepted the call ornot. All things being equal, it is probably more likely that the userwould not accept the call while on an emergency call, when compared to aregular call. Calls placed immediately prior to the 911 call (e.g., tothe caller's doctor), however, may prompt the user to answer the calland place the PSAP 110 a on hold or hang up with the PSAP 110 a. Thus,the caller is given the option to reject random calls that just happenedto be placed within the caller-specific guard timer, for example; yet,accept calls that are relevant to the pending emergency or that the userotherwise wishes to answer.

To this end, at 316, the user can have the normal choices to place theemergency call on hold or to hang up. The user may wish to switch overto Caller 1 briefly, for example, to give a loved one an update and thenswitch back to the emergency call. In some examples, Caller 1 may bebetter equipped to help the user than the PSAP operator. In this case,the user can simply hang up the emergency call and take the incomingcall.

At 318, if, on the other hand the (1) user (or rather, the UE 102) hasnever called the number or (2) the caller-specific guard timer for thatnumber has expired, or (3) the user rejects the call, the caller 110 canbe sent to voicemail to enable the caller 110 to leave a message. Thus,even for calls with unexpired guard timers, the user has the choice toanswer the call or remain on the emergency call depending oncircumstances. If the user is on hold with the PSAP or in queue, forexample, the user may choose to answer the call. If the user is activelyspeaking with a PSAP operator, on the other hand, the user may choose tolet the caller 110 go to voicemail. In the case of a caller for which nocaller-specific guard timer is set (i.e., the user has not called thecaller in the last 5 minutes or has never called the caller), however,the call is handled in the usual manner.

As shown in FIG. 4, therefore, examples of the present disclosure cancomprise a method 400 for providing a proactive guard timer that is notcaller specific. In his configuration, a proactive guard timer can beset at the conclusion of an initial 911 call. If the user then calls 911again, all calls (as opposed to calls from a specific caller) that comeinto the UE 102 within the proactive guard timer are sent to the UE 102(e.g., to call-waiting). Once the proactive guard timer expires, if theuser is still on the 911 call, all calls are handled in the usualmanner. At least one benefit to this method 400 is that it is likelythat the incoming call is from the PSAP 110 a in response to the initial911 call from which the user hung up.

To this end, at 402, the user (or rather, the UE 102) can place Call 1to the PSAP 110 a. At 404, the user can hang up on Call 1. This may bebecause the PSAP placed the call on hold, didn't answer, or placed theuser in a long queue, among other things.

Regardless, at 406, the method 400 can set the proactive guard timer.The proactive guard timer can be for any suitable time, which can bechosen by the user, the app provider, the service provider, ormanufacturer, among other things. The proactive guard timer basicallysays, “If the user calls 911 again, any caller that calls prior to theproactive guard timer will be put through to the UE 102. Any incomingcalls after the proactive guard timer has expired are handled in theusual manner.” To this end, at 408, the user can place Call 2 to thePSAP 110 a (though not necessarily the same PSAP 110 a).

At 410, the user can receive a call from Caller 1. In this case,however, the identity of Caller 1 is irrelevant. In other words, it doesnot matter if the user has called Caller 1 recently, or at all, justthat the proactive guard timer has not expired. Thus, at 412, the method400 can determine if the proactive guard timer has expired. Again, thisstep has nothing to do with who is calling, just when they are calling.Beneficially, Caller 1 is likely the PSAP 110 a calling back fromCall 1. Of course, it is also possible that a telemarketer would justhappen to call at this particular time, though this is a relatively slimpossibility.

At 414, if the proactive guard timer has not expired, the method 400 cansend the call through to the UE 102, activating call-waiting. Thus, theuser is given the opportunity to accept or reject the call—even thoughthey are on an emergency call.

At 416, the method 400 can determine if the user accepted the call ornot. All things being equal, it is probably more likely that the userwould not accept the call while on an emergency call, when compared to aregular call. In this case, however, it is fairly likely that Caller 1is the PSAP 110 a calling back from Call 1. Thus, the caller is giventhe option to reject random calls that just happened to be receivedwithin the proactive guard timer, for example; yet, accept calls thatare relevant to the pending emergency or that the user otherwise wishesto answer.

To this end, at 418, the user can have the normal choices to place theemergency call on hold or to hang up. In this case, because Caller 1 islikely the PSAP 110 a the user was trying to contact in the first place,the user may wish to accept the incoming call and hang up Call 2. Asmentioned above, this can expedite the process for both the user and thePSAP 110 a. Of course, the user may also have called a loved one,doctor, etc. just prior to Call 1. Thus, the user may wish to switchover to Caller 1 briefly, for example, to give a loved one an update andthen switch back to the emergency call. In some examples, Caller 1 maybe better equipped to help the user than the PSAP operator. In thiscase, the user can simply hang up the emergency call and take theincoming call.

At 420, once the proactive guard timer expires, all incoming calls canbe handled in the usual manner. In addition, if the user rejects Caller1, Caller 1 can be sent to voicemail to enable Caller 1 to leave amessage. Thus, even prior to the proactive guard timer expiring, theuser maintains the choice to answer the call or remain on the emergencycall depending on circumstances. If the user is on hold with the PSAP orin queue, for example, the user may choose to answer the call regardlessof who it is. If the user is actively speaking with a PSAP operator, onthe other hand, the user may choose to let the caller 110 go tovoicemail regardless of who it is.

These methods 200, 300, 400 could be performed by an app on the UE 102or the OS of the UE 102, as described above. The methods 200, 300, 400could just as easily be carried out by a component of the IMS 104,however. An TAS, for example, could monitor calls to and from the UE102, maintain the retroactive guard timer(s), and route callsappropriately. Similarly, an MSC, 3GPP AAA server, or other networkentity could handle some, or all, of the methods 200, 300, 400. To thisend, the methods 200, 300, 400 discussed above are purely illustrativeand not intended to limit the disclosure.

As shown in FIG. 5, some or all of the system 100 and methods 200, 300,400 can be performed by, and/or used in conjunction with, a UE 102 thatcan comprise a variety of electronic devices. For clarity, the UE 102 isdescribed herein generally as a cell phone or smart phone. One of skillin the art will recognize, however, that the system 100 and methods 200,300, 400 can also be used with a variety of other electronic devices,such as, for example, tablet computers, laptops, desktops, and othernetwork (e.g., cellular or IP network) connected devices from which a911 call can be placed. These devices are referred to collectivelyherein as UEs 102.

The UEs 102 can comprise a number of components to execute theabove-mentioned functions and apps. As discussed below, the UEs 102 cancomprise memory 502 including many common features such as, for example,the contacts 504, calendar 506, the aforementioned call log (or, callhistory) 508, and the operating system (OS) 510. In this case, thememory 502 can also store a call-handling app 512 and the guard timer514.

The UEs 102 can also comprise one or more processors 516. In someimplementations, the processor(s) 516 is a central processing unit(CPU), a graphics processing unit (GPU), or both CPU and GPU, or anyother sort of processing unit. The UEs 102 can also include one or moreof removable storage 518, non-removable storage 520, transceiver(s) 522,output device(s) 524, and input device(s) 526. In some examples, such asfor cellular communication devices, the UEs 102 can also include asubscriber identification module (SIM) 528 including an InternationalMobile Subscriber Identity (IMSI), and other relevant information.

In various implementations, the memory 502 can be volatile (such asrandom access memory (RAM)), non-volatile (such as read only memory(ROM), flash memory, etc.), or some combination of the two. The memory502 can include all, or part, of the functions 504, 506, 508, 512, 514and the OS 510 for the UEs 102, among other things.

The memory 502 can also comprise contacts 504, which can include names,numbers, addresses, and other information about the user's business andpersonal acquaintances, among other things. In some examples, the memory502 can also include a calendar 506, or other software, to enable theuser to track appointments and calls, schedule meetings, and providesimilar functions. In some examples, the memory 502 can also comprisethe call log 508 of calls received, missed, and placed from the UE 102.As usual, the call log 508 can include timestamps for each call for useby the system 100. Of course, the memory 502 can also include othersoftware such as, for example, e-mail, text messaging, social media, andutilities (e.g., calculators, clocks, compasses, etc.).

The memory 502 can also include the OS 510. Of course, the OS 510 variesdepending on the manufacturer of the UE 102 and currently comprises, forexample, iOS 10.3.2 for Apple products and Nougat for Android products.The OS 510 contains the modules and software that supports a computer'sbasic functions, such as scheduling tasks, executing applications, andcontrolling peripherals.

As mentioned above, the UE can also include a call-handling module, orcall-handling app 512. The call-handling app 512 can perform some or allof the functions discussed above with respect to the methods 200, 300,400, 400 for call handling on the UE 102. Thus, the call-handling app512 can also have access to the call log 508 and guard timer 514. Thus,the call-handling app 512 can be activated when the user dials 911, forexample, or can have a listening function that monitors thetransceiver(s) 522, for example, and activates when 911 is dialed (or alocal PSAP 110 a number is dialed, if applicable).

Thus, the call-handling app 512 can determine that the UE 102 has dialed911, for example, and then await incoming calls. If an incoming callcomes in during the 911 call, the call-handling app 512 can consult the(retroactive) guard timer 514 to determine the predetermined time window(e.g., five minutes) and then consult the call log 508 for calls madewithin that window. Using this information, the call-handling app 512can determine if the incoming call should be sent to voicemail or theuser. If the incoming call was placed to the caller within thepredetermined time window prior to the user dialing 911, for example,the call-handling app 512 can activate call-waiting to enable the userto accept, reject, or simply ignore the incoming call. Similarly, insome examples, the call-handling app 512 can determine if the proactiveguard timer 514 has expired and route calls accordingly.

The UEs 102 may also include additional data storage devices (removableand/or non-removable) such as, for example, magnetic disks, opticaldisks, or tape. Such additional storage is illustrated in FIG. 5 byremovable storage 518 and non-removable storage 520. The removablestorage 518 and non-removable storage 520 can store some, or all, of thefunctions 504, 506, 508, 510.

Non-transitory computer-readable media may include volatile andnonvolatile, removable and non-removable tangible, physical mediaimplemented in technology for storage of information, such as computerreadable instructions, data structures, program modules, or other data.The memory 502, removable storage 518, and non-removable storage 520 areall examples of non-transitory computer-readable media. Non-transitorycomputer-readable media include, but are not limited to, RAM, ROM,electronically erasable programmable ROM (EEPROM), flash memory or othermemory technology, compact disc ROM (CD-ROM), digital versatile disks(DVD) or other optical storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othertangible, physical medium which can be used to store the desiredinformation and which can be accessed by the UEs 102. Any suchnon-transitory computer-readable media may be part of the UEs 102 or maybe a separate database, databank, remote server, or cloud-based server.

In some implementations, the transceiver(s) 522 include any sort oftransceivers known in the art. In some examples, the transceiver(s) 522can include wireless modem(s) to facilitate wireless connectivity withthe other UEs, the Internet, and/or an intranet via a cellularconnection. Further, the transceiver(s) 522 may include a radiotransceiver that performs the function of transmitting and receivingradio frequency communications via an antenna (e.g., Wi-Fi orBluetooth®). In other examples, the transceiver(s) 522 may include wiredcommunication components, such as a wired modem or Ethernet port, forcommunicating with the other UEs or the provider's Internet-basednetwork.

In some implementations, the output device(s) 524 include any sort ofoutput devices known in the art, such as a display (e.g., a liquidcrystal or thin-film transistor (TFT) display), a touchscreen display,speakers, a vibrating mechanism, or a tactile feedback mechanism. Insome examples, the output devices can play various sounds based on, forexample, whether the UEs 102 is connected to a network, the type of callbeing received (e.g., video calls vs. voice calls), the number of activecalls, etc. Output device(s) 524 also include ports for one or moreperipheral devices, such as headphones, peripheral speakers, or aperipheral display.

In various implementations, input device(s) 526 include any sort ofinput devices known in the art. For example, the input device(s) 526 mayinclude a camera, a microphone, a keyboard/keypad, or a touch-sensitivedisplay. A keyboard/keypad may be a standard push button alphanumeric,multi-key keyboard (such as a conventional QWERTY keyboard), virtualcontrols on a touchscreen, or one or more other types of keys orbuttons, and may also include a joystick, wheel, and/or designatednavigation buttons, or the like.

As shown in FIG. 6, the system 100 and methods 200, 300, 400 can also beused in conjunction with a network entity, or server 600, of the IMS104, which can comprise a variety of electronic devices. As mentionedabove, this server 600 can comprise a TAS, 3GPP AAA server, HLR, HSS, oranother server or component associated with the IMS 104.

The server 600 can comprise a number of components to execute theabove-mentioned functions and apps. As discussed below, the server 600can comprise memory 602 including many common features such as, forexample, the OS 604, call routing module 606, and the guard timer 608.

The server 600 can also comprise one or more processors 610. In someimplementations, the processor(s) 610 can be a central processing unit(CPU), a graphics processing unit (GPU), or both CPU and GPU, or anyother sort of processing unit. The server 600 can also include one ormore of removable storage 612, non-removable storage 614, transceiver(s)616, output device(s) 618, and input device(s) 620.

In various implementations, the memory 602 can be volatile (such asrandom access memory (RAM)), non-volatile (such as read only memory(ROM), flash memory, etc.), or some combination of the two. The memory602 can include all, or part, of the functions 606, 608 for the server600, among other things. The memory 602 can also include the OS 604. Ofcourse, the OS 604 varies depending on the manufacturer of the server600 and the type of component. Many servers, for example, run Linux orWindows Server. Dedicated cellular routing servers may run specifictelecommunications OS 604. The OS 604 contains the modules and softwarethat supports a computer's basic functions, such as scheduling tasks,executing applications, and controlling peripherals.

In some examples, depending in the server's function, the server 600 canalso comprise a call routing module 606. The server 600 can comprise anMSC 618 (discussed below), for example, responsible for routing voicecalls from one UE 102 to another or to a landline. Regardless, theserver 600 can route calls through the IMS 104 to their destination. Insome examples, the call routing module 606 can also work in concert withthe white list 608 to affect proper call handling when a user is on anemergency call—routing recent calls to the UE 102 and other calls tovoicemail.

In some examples, the server 600 can also comprise the guard timer 608.As mentioned above, the optimized call handling during e911 calls can behandled on the UE 102 or on the IMS 104 (i.e., the network side). In thecase of network implementation, the server 600 can determine whether theuser is on a 911 call. If, during the 911 call, the user receives asecond call, the server 600 can consult the guard timer 608 and a calllog associated with the user's UE 102 to determine whether a caller wascalled within the predetermined time period (retroactive guard timer) orwhether the guard timer has expired (proactive guard timer). If thecaller was called on the UE 102 prior to the 911 call and within thepredetermined time window, for example, then the caller can be sentthrough to the UE 102 to activate call-waiting, as discussed above.

The server 600 may also include additional data storage devices(removable and/or non-removable) such as, for example, magnetic disks,optical disks, or tape. Such additional storage is illustrated in FIG. 6by removable storage 612 and non-removable storage 614. The removablestorage 612 and non-removable storage 614 can store some, or all, of theOS 604 and functions 606, 608.

Non-transitory computer-readable media may include volatile andnonvolatile, removable and non-removable tangible, physical mediaimplemented in technology for storage of information, such as computerreadable instructions, data structures, program modules, or other data.The memory 602, removable storage 612, and non-removable storage 614 areall examples of non-transitory computer-readable media. Non-transitorycomputer-readable media include, but are not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, DVDs or otheroptical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other tangible,physical medium which can be used to store the desired information andwhich can be accessed by the server 600. Any such non-transitorycomputer-readable media may be part of the server 600 or may be aseparate database, databank, remote server, or cloud-based server.

In some implementations, the transceiver(s) 616 include any sort oftransceivers known in the art. In some examples, the transceiver(s) 616can include wireless modem(s) to facilitate wireless connectivity withthe other UEs, the Internet, and/or an intranet via a cellularconnection. Further, the transceiver(s) 616 may include a radiotransceiver that performs the function of transmitting and receivingradio frequency communications via an antenna (e.g., Wi-Fi orBluetooth®). In other examples, the transceiver(s) 616 may include wiredcommunication components, such as a wired modem or Ethernet port, forcommunicating with the other UEs or the provider's Internet-basednetwork.

In some implementations, the output device(s) 618 include any sort ofoutput devices known in the art, such as a display (e.g., a liquidcrystal or thin-film transistor (TFT) display), a touchscreen display,speakers, a vibrating mechanism, or a tactile feedback mechanism. Insome examples, the output devices can play various sounds based on, forexample, whether the server 600 is connected to a network, the type ofcall being received (e.g., video calls vs. voice calls), the number ofactive calls, etc. Output device(s) 618 also include ports for one ormore peripheral devices, such as headphones, peripheral speakers, or aperipheral display.

In various implementations, input device(s) 620 include any sort ofinput devices known in the art. For example, the input device(s) 620 mayinclude a camera, a microphone, a keyboard/keypad, or a touch-sensitivedisplay. A keyboard/keypad may be a standard push button alphanumeric,multi-key keyboard (such as a conventional QWERTY keyboard), virtualcontrols on a touchscreen, or one or more other types of keys orbuttons, and may also include a joystick, wheel, and/or designatednavigation buttons, or the like.

FIG. 7 depicts a conventional cellular network 700 including 2G 702, 3G704, and 4G long-term evolution (LTE) 706 components. Of course, futuretechnologies, such as, for example, 7G and device-to-device (D2D)components could also be included and are contemplated herein. Asmentioned above, many of the “back-end” components of the network 700could handle some, or all, of the system 100 and methods 200, 300, 400associated with optimized call handling during e911 calls. Indeed, some,or all, of the aforementioned call routing module 507 and white list 508components could be located on one or more of, for example, the HLR/HSS722, the 3GPP AAA server 726, or other components.

As is known in the art, data can be routed from the Internet or othersources using a circuit switched modem connection (or non-3GPPconnection) 708, which provides relatively low data rates, or via IPbased packet switched 710 connections, which results is higherbandwidth. The LTE system 706, which is purely IP based, essentially“flattens” the architecture, with data going straight from the internetto the service architecture evolution gateway (SAE GW) 712 to evolvedNode B transceivers 706, enabling higher throughput. Many UEs 102 alsohave wireless local area network (WLAN) 714 capabilities, in some casesenabling even higher throughput. In some cases, cellular carriers mayuse WLAN communications in addition to, or instead of, cellularcommunications to supplement bandwidth.

The serving GPRS support node (SGSN) 716 is a main component of thegeneral packet radio service (GPRS) network, which handles all packetswitched data within the network 700—e.g. the mobility management andauthentication of the users. The MSC 718 essentially performs the samefunctions as the SGSN 716 for voice traffic. The MSC 718 is the primaryservice delivery node for global system for mobile communication (GSM)and code division multiple access (CDMA), responsible for routing voicecalls and short messaging service (SMS) messages, as well as otherservices (such as conference calls, fax, and circuit switched data). TheMSC 718 sets up and releases the end-to-end connection, handles mobilityand hand-over requirements during the call, and takes care of chargingand real time pre-paid account monitoring.

Similarly, the mobility management entity (MME) 720 is the keycontrol-node for the 4G LTE network 706. It is responsible for idle modeUE 102 paging and tagging procedures including retransmissions. The MME720 is involved in the bearer activation/deactivation process and isalso responsible for choosing the SAE GW 712 for the UE 102 at theinitial attach and at time of intra-LTE handover involving Core Network(CN) node relocation (i.e., switching from one cell tower to the nextwhen traveling). The MME 720 is responsible for authenticating the user(by interacting with the HSS 722 discussed below). The Non-AccessStratum (NAS) signaling terminates at the MME 720 and it is alsoresponsible for generation and allocation of temporary identities to UE102. The MME 720 also checks the authorization of the UE 102 to camp onthe service provider's HPLMN or VPLMN and enforces UE 102 roamingrestrictions on the VPLMN. The MME 720 is the termination point in thenetwork for ciphering/integrity protection for NAS signaling and handlesthe security key management. The MME 720 also provides the control planefunction for mobility between LTE 706 and 2G 702/3G 704 access networkswith the S3 interface terminating at the MME 720 from the SGSN 716. TheMME 720 also terminates the S7a interface towards the home HSS 722 forroaming UEs 102.

The HSS/HLR 722 is a central database that contains user-related andsubscription-related information. The functions of the HSS/HLR 722include functionalities such as mobility management, call and sessionestablishment support, user authentication and access authorization. TheHSS, which is used for LTE connections, is based on the previous HLR andAuthentication Center (AuC) from CGMA and GSM technologies, with eachserving substantially the same functions for their respective networks.

The policy and charging rules unction (PCRF) 724 is a software node thatdetermines policy rules in the network 700. The PCRF 724 is generallyoperates at the network core and accesses subscriber databases (e.g.,the HSS/HLR 722) and other specialized functions, such as enhanced e911call handling, in a centralized manner. The PCRF 724 is the main part ofthe network 700 that aggregates information to and from the network 700and other sources (e.g., IP networks 710). The PCRF 724 can support thecreation of rules and then can automatically make policy decisions foreach subscriber active on the network 700. The PCRF 724 can also beintegrated with different platforms like billing, rating, charging, andsubscriber database or can also be deployed as a standalone entity.

Finally, the 3GPP AAA server 726 performs authentication, authorization,and accounting (AAA) functions and may also act as an AAA proxy server.For WLAN 714 access to (3GPP) IP networks 710 the 3GPP AAA Server 726provides authorization, policy enforcement, and routing information tovarious WLAN components. The 3GPP AAA Server 726 can generate and reportcharging/accounting information, performs offline charging control forthe WLAN 714, and perform various protocol conversions when necessary.

As shown, in some examples, the 3GPP AAA server 726 can contain some, orall, of the components of the guard timer for enhanced e911 callhandling. The 3GPP AAA server 726 can contain, for example, the callrouting module 507 and the white list 508, among other things. Ofcourse, as mentioned above, other components (e.g., the HSS/HLR 722)could also include some, or all, of the guard timer for enhanced e911call handling.

FIG. 8 includes a more detailed view of the IMS 104. As shown, the IMS104 includes a number of network components for routing signals, storingsubscriber information, and connecting across various subsystems andnetwork types. As discussed above, the IMS 104 is built on SIP as thebase to further support packaging of voice, video, data, fixed, andmobile services on a single platform to end users. It enablescommunications across multiple types of networks, including cellular,satellite, broadband, cable, and fixed networks, and enables thecreation of efficient interoperating networks.

As mentioned above, the IMS 104 provides interoperability for UEs 102and other devices across multiple platforms including, for example, 2G702, 3G 704, 4G 706, IP 710 networks. The IMS 104 also includes somecomponents already discussed in the more general FIG. 7. These include,for example, the PCRF 724, HSS 722 and SAE GW 712.

The IMS 104 also includes, however, a proxy-call session controlfunction (P-CSCF) 802. The P-CSCF 802 is the entry point to the IMS 104and serves as the outbound proxy server for the UE 102. The UE 102attaches to the P-CSCF 802 prior to performing IMS registrations andinitiating SIP sessions. The P-CSCF 802 may be in the home domain of theIMS operator, or it may be in the visiting domain, where the UE 102 iscurrently roaming. For attachment to a given P-CSCF 802, the UE performsP-CSCF 802 discovery procedures. Attachment to the P-CSCF 802 enablesthe UE 102 to initiate registrations and sessions with the IMS 104.

The IMS 104 also includes an interrogating-call session control function(I-CSCF) 804. The I-CSCF 804 acts as an inbound SIP proxy server in theIMS 104. During IMS registrations, the I-CSCF 804 queries the HSS 722 toselect the appropriate S-CSCF 806 (discussed below) which can serve theUE 102. During IMS 104 sessions, the I-CSCF 804 acts as the entry pointto terminating session requests. The I-CSCF 804 routes the incomingsession requests to the S-CSCF 806 of the called party.

The IMS 104 also includes a serving-call session control function(S-CSCF) 806. The S-CSCF 806 acts as a registrar server, and in somecases as a redirect server. The S-CSCF 806 facilitates the routing pathfor mobile originated or mobile terminated session requests. The S-CSCF806 also interacts with various components for playing tones andannouncements, among other things.

The IMS 104 also includes a breakout gateway control function (BGCF)808. The BGCF 808 is the IMS 104 element that selects the network inwhich PSTN 818 (discussed below) breakout is to occur. If the breakoutis to occur in the same network as the BGCF 808, for example, then theBGCF 808 selects a Media Gateway Control Function (MGCF) 814 (alsodiscussed below) that will be responsible for interworking with the PSTN818. The MGCF 814 then receives the SIP signaling from the BGCF 808.

The IMS 104 also includes a subscriber location function (SLF) 810. TheSLF 810 provides information about the HSS 722 that is associated with aparticular user profile. It is generally implemented using a database.If the IMS 104 contains more than one HSS 722, I-CSCF 804 and S-CSCF 806will communicate with SLF 810 to locate the appropriate HSS 722 based onthe user profile.

The IMS 104 also includes the aforementioned TAS 812. As the nameimplies, the TAS 812, sometimes known in a telephony context only as anapplication server (AS), is a component used to provide telephonyapplications and additional multimedia functions. The TAS 812 caninclude any entity in a telephone network that carries out functionsthat are not directly related to the routing of messages through thenetwork. Such functions can include, for example, in-network answeringmachines, automatic call forwarding, conference bridges and other typesof applications, including the systems 100 and methods 200, 300, 400,400 discussed herein.

The IMS 104 also includes a media gateway controller function (MGCF)814. The MGCF 814 is a SIP endpoint that handles call control protocolconversion between SIP and ISDN user part (ISUP)/Bearer-Independent CallControl (BICC) and interfaces with the SAE GW 712 over Stream ControlTransmission Protocol (SCTP). The MGCF 814 also controls the resourcesin a Media Gateway (MGW) 816 across an H.248 interface (discussedbelow).

The IMS 104 also includes a (MGW) 816. The MGW 816 is a translationdevice or service that converts media streams between disparatetelecommunications technologies such as POTS, SSB, Next GenerationNetworks (2G 702, 3G 704, and 4G 706) or private branch exchange (PBX)systems.

Finally, the IMS 104 also includes a public switched telephone network(PSTN) 818. The PSTN 818 is the world's collection of interconnectedvoice-oriented public telephone networks, both commercial andgovernment-owned. It's also referred to as the Plain Old TelephoneService (POTS). With respect to IP phones 710, for example, the PSTN 818actually furnishes much of the Internet's long-distance infrastructure.Because Internet service providers (ISPs) pay the long-distanceproviders for access to their infrastructure and share the circuitsamong many users through packet-switching (discussed above), Internetusers avoid having to pay usage tolls to anyone other than their ISPs.

While several possible examples are disclosed above, examples of thepresent disclosure are not so limited. For instance, while the systemsand methods above are discussed with reference to use with cellularcommunications, the systems and methods can be used with other types ofwired and wireless communications. In addition, while various functionsare discussed as being performed on the UE 102 and/or various componentson the IMS 104, other components could perform the same or similarfunctions without departing from the spirit of the invention.

The specific configurations, machines, and the size and shape of variouselements can be varied according to particular design specifications orconstraints requiring a UE 102, server 500, system 100, or method 200,300, 400 constructed according to the principles of this disclosure.Such changes are intended to be embraced within the scope of thisdisclosure. The presently disclosed examples, therefore, are consideredin all respects to be illustrative and not restrictive. The scope of thedisclosure is indicated by the appended claims, rather than theforegoing description, and all changes that come within the meaning andrange of equivalents thereof are intended to be embraced therein.

What is claimed is:
 1. A method comprising: determining, by a processorof a user equipment (UE), that a transceiver on the UE has disconnectedfrom a first call to a public safety answering point (PSAP); starting,by the processor, a proactive guard timer set to expire in apredetermined amount of time; determining, by the processor, that thetransceiver has connected to a second call to a PSAP; receiving, at thetransceiver, an incoming call for the UE while the transceiver is stillconnected to the PSAP; determining, by the processor, whether theproactive guard time has expired; and either: activating, by theprocessor, call-waiting on the UE for the incoming call when theproactive guard timer has not expired; or sending, by the processor orthe transceiver, the incoming call directly to voicemail if theproactive guard timer has expired.
 2. The method of claim 1, wherein thepredetermined amount of time is 180 seconds.
 3. The method of claim 1,wherein determining that the transceiver has connected to the PSAPcomprises receiving, at the processor, a signal from a dialer on the UEthat 911 has been dialed on the dialer.
 4. The method of claim 1,wherein determining that the transceiver has connected to the PSAPcomprises: receiving, at the processor, a signal from a dialer on the UEincluding a phone number that has been dialed from the UE; anddetermining, with the processor, that the phone number is included in alist of phone numbers for local PSAPs.
 5. The method of claim 1, furthercomprising: determining, by the processor, whether a number associatedwith the incoming call is associated with a PSAP; and either:activating, by the processor, call-waiting on the UE for the incomingcall when the proactive guard timer has not expired and the incomingcall is associated with the PSAP; or sending, by the processor or thetransceiver, the incoming call directly to voicemail if at least one ofthe proactive guard timer has expired or the incoming call is notassociated with the PSAP.
 6. The method of claim 1, further comprising:receiving, at the transceiver, a signal to cause the UE to disconnectfrom the second call; and reactivating call-waiting for all incomingcalls.
 7. A method comprising: determining, by a processor of a networkentity associated with a telecommunications network, that a userequipment (UE) has disconnected from a first call to a public safetyanswering point (PSAP); starting, by the processor, a proactive guardtimer set to expire in a predetermined amount of time; determining, bythe processor, that the UE has connected to a second call to a PSAP;receiving, at a transceiver of the network entity, an incoming call forthe UE while the UE is still connected to the PSAP; determining, by theprocessor, whether the proactive guard time has expired; and either:sending, with the transceiver, the incoming call to the UE when theproactive guard timer has not expired; or sending, with the transceiver,the incoming call directly to a voicemail server if the proactive guardtimer has expired.
 8. The method of claim 7, further comprising:determining, by the processor, whether a number associated with theincoming call is associated with a PSAP; and either: sending, by thetransceiver, the incoming call to the UE when the proactive guard timerhas not expired and the incoming call is associated with the PSAP; orsending, by the transceiver, the incoming call directly to the voicemailserver if at least one of the proactive guard timer has expired or theincoming call is not associated with the PSAP.
 9. The method of claim 7,wherein determining that the UE is connected to the PSAP comprisesreceiving, at the transceiver of the network entity, a sessioninitiation protocol (SIP) message from the UE including a response codeindicating that the UE is engaged in a 911 call.
 10. The method of claim7, further comprising: receiving, with the transceiver, another SIPmessage from the UE indicating that the UE has disconnected from thesecond call to the PSAP; and reactivating call-waiting for the UE forall incoming calls.
 11. The method of claim 7, wherein determining thatthe UE is connected to the PSAP comprises receiving, at the transceiverof the network entity, a SIP message from the PSAP including a responsecode indicating that the UE is connected to the PSAP.
 12. The method ofclaim 7, wherein sending the incoming call to the UE activatescall-waiting on the UE to enable the incoming call to be accepted orrejected at the UE.
 13. The method of claim 7, wherein the networkentity comprises a mobile switching center (MSC).
 14. The method ofclaim 13, wherein determining that the UE is connected to the PSAPcomprises: determining, with the processor of the MSC, a numberassociated with the second call; and determining, with the processor,that the number is included in a list associated with local PSAPs.
 15. Auser equipment (UE) comprising: a processor; a transceiver; and memorycomprising program instructions that, when executed by the processor,cause the processor to: determine that the transceiver has disconnectedfrom a first call to a public safety answering point (PSAP); start aproactive guard timer set to expire in a predetermined amount of time;determine that the transceiver has connected to a second call to a PSAP;receive, at the transceiver, an incoming call for the UE while thetransceiver is still connected to the PSAP; determine whether theproactive guard time has expired; and either: activate call-waiting onthe UE for the incoming call when the proactive guard timer has notexpired; or send the incoming call directly to voicemail if theproactive guard timer has expired.
 16. The UE of claim 15, wherein thepredetermined amount of time is 300 seconds.
 17. The UE of claim 15,wherein determining that the transceiver has connected to the PSAPcomprises receiving, by the processor, a signal from a dialer on the UEthat 911 has been dialed on the dialer.
 18. The UE of claim 15, theprogram instructions further causing the processor to: determine whethera number associated with the incoming call is associated with a PSAP;and either: activate call-waiting on the UE for the incoming call whenthe proactive guard timer has not expired and the incoming call isassociated with the PSAP; or send the incoming call directly tovoicemail if at least one of the proactive guard timer has expired orthe incoming call is not associated with the PSAP.
 19. The UE of claim18, wherein the memory further includes a list of numbers associatedwith local PSAPs; and wherein determining whether the number associatedwith the incoming call is associated with the PSAP comprises: receiving,from the transceiver, a number associated with the incoming call;comparing the number with the list of numbers associated with the localPSAPs; and determining whether the number is included in the list ofnumbers associated with the local PSAPs.
 20. The UE of claim 15, whereinthe predetermined amount of time is 120 seconds.
 21. A network entityassociated with a telecommunications network comprising: a processor; atransceiver; and memory comprising program instructions that, whenexecuted by the processor, cause the processor to perform actscomprising: determining that a user equipment (UE) has disconnected froma first call to a public safety answering point (PSAP); starting aproactive guard timer set to expire in a predetermined amount of time;determining that the UE has connected to a second call to a PSAP;receiving, at the transceiver, an incoming call for the UE while the UEis still connected to the PSAP; determining whether the proactive guardtime has expired; and either: sending, with the transceiver, theincoming call to the UE when the proactive guard timer has not expired;or sending, with the transceiver, the incoming call directly to avoicemail server if the proactive guard timer has expired.
 22. Thenetwork entity of claim 21, the program instructions further causing theprocessor to perform acts comprising: determining, by the processor,whether a number associated with the incoming call is associated with aPSAP; and either: sending, by the transceiver, the incoming call to theUE when the proactive guard timer has not expired and the incoming callis associated with the PSAP; or sending, by the transceiver, theincoming call directly to the voicemail server if at least one of theproactive guard timer has expired or the incoming call is not associatedwith the PSAP.
 23. The network entity of claim 21, wherein determiningthat the UE is connected to the PSAP comprises receiving, at thetransceiver, a session initiation protocol (SIP) message from the UEincluding a response code indicating that the UE is engaged in a 911call.
 24. The network entity of claim 21, the program instructionsfurther causing the processor to perform acts comprising: receiving,with the transceiver, another SIP message from the UE indicating thatthe UE has disconnected from the second call to the PSAP; andreactivating call-waiting for the UE for all incoming calls.
 25. Thenetwork entity of claim 21, wherein sending the incoming call to the UEactivates call-waiting on the UE to enable the incoming call to beaccepted or rejected at the UE.
 26. The network entity of claim 21,wherein the network entity comprises one of a proxy call session controlfunction (P-CSCF) or a mobile switching center (MSC).